It is generally known that safety measures have to be taken with automatically operable doors (and gates) so that obstacles or persons are not hit by the moving door closing edge and may be damaged or injured therewith.
For this purpose, as is well-known, contact edge protections have been arranged at the leading and/or abutting edges of automatically operated doors, which, on occurrence of a counter force, i.e. the detection of an obstacle, stop the door drive and/or even effect “relief” in the sense of a reversion (reversal) of the direction of movement.
The disadvantage of such tactile systems, i.e. of systems responding to contact with the object, consists in that contact occurs at any rate before the sensor can effect stopping and/or reversing of the direction of movement of the door drive. Possibly, at least slight injuries or damages will thus occur.
Another known safety device provides that light barriers and/or light grids consisting of a plurality of light barriers are applied within the door closing plane to produce a safety light curtain. Advantageous systems in this respect are described in EP 0 902 157 A2 and in EP 0 902 158 A2.
A system of this kind, however, requires the detection of the position of the leading edge of the door leaf so as to avoid erroneous object detection by the door leaf. For this purpose, sequential ignoring of particular light barriers is usually provided, which then enables acting with one light grid only. Examples therefor are also found in the documents WO 2014/040583 A1 and DE 20 2014 101 131 U1.
DE 10 2007 050 334 A1, however, describes a somewhat different system in which the entering of an obstacle in the door closing plane is detected due to an interruption of the detector beam, which causes the stopping and/or reversing of the motor drive. For this purpose, a detector beam is pivoted over an area of preferably 90° in the door closing plane close to a corner of the door opening by means of a distance measurement scanning detector. By means of the running time of detected distance measurement values it is detected, by comparison with previously stored limit values, whether a disturbing object is present in the monitored area, wherein the occurrence of the object results in a reduction of the running time of the detector beam. Since the optical safety system is positioned in the door closing plane here, too, the current position of the leading edge of the door leaf is also considered by means of previously determined standard values so as to avoid false alarms.
However, also these kinds of safeguarding of dangerous places in the movement area of a door leaf are, like the systems responding to contact with an object, often not sufficient for avoiding collisions in a reliable manner. If, for instance, a person approaches and the door leaf is moving at the same time, it can, due to the technologically given reaction time of the safety system, not be excluded reliably that the head of a person and the leading edge of the door leaf may collide in the course of their movements. Furthermore, a person may bump on a large area of the door leaf while it is moving, without this being detected by these known safety systems. As experience has shown, slight injuries, especially on the head, cannot always be avoided in this case.
Another possibility of safeguarding consists in applying sensors above the door opening, said sensors generating, shortly in front of the door closing plane, a safety field which reaches down to the ground and may also have a spatial depth extension. Infrared or ultrasound sensors as well as radar sensors are common for this purpose. Moreover, it is also known to detect further into the forefield of the door opening and to thus detect the approaching of objects or persons. A safe and advantageous method in this respect is described in EP 1 470 314 A1.
Motion sensors, however, have the disadvantage that they do not detect stationary objects, such as persons standing close to the door leaf Presence sensors, on the contrary, are susceptible to environmental influences and lighting conditions. Moreover, both kinds of sensors often have the problem that they do not cover the forefield in front of the door leaf completely since it is, due to the local conditions, for instance, not always possible to place the sensor optimally. It is then absolutely possibly to approach the door without being detected.
The situation is particularly problematic with door arrangements which are installed in constricted rooms and/or in applications where persons constantly work in the direct vicinity of the door. This is frequently the case, for example, with doors in a sales room and in a storage area in supermarkets. On the one hand, it is not possible here that the forefield monitoring is performed across a large area since the forefield is used as a production and storage area, and, on the other hand, these are often comparatively low doors, so that the possibilities of reaction to the closing door leaf are relatively minor here. Injuries of persons cannot always be excluded in a reliable manner in this case.
Moreover, it also happens that persons lean against a closed door leaf and are then, when the door surprisingly opens, hit on the chin or the nose, for instance, by the massive closure element. Sometimes, employees also prop themselves with their arms on the door frame while the door is open, which may possibly result in fingers being bruised in the course of the closing process.
Another specific problem has occurred with door arrangements used as emergency exits or in escape ways. Here, it is necessary that they mandatorily open when being approached, so that the escape way becomes free. This is regularly implemented by monitoring the forefield of the door. In the case of the conventional forefield sensors the above-described detection loopholes remain, so that a lateral approaching of escaping persons may be possible without this being detected. For the escaping persons especially the circumstance is a problem that, in the case of larger agglomerations of people, a knot of people may press against the door leaf and that the opening thereof is then completely prevented by the pressure.
Another known solution which guarantees suitable protection of persons or from damage to the door arrangement and/or to other things consists in applying light barriers and/or light grids consisting of a plurality of light barriers shortly in front of and behind the door closing plane and to thus produce a safety light curtain on both sides of the door leaf movement plane.
DE 10 2008 017 244 A1 moreover discloses a method and a device for controlling a vertically or horizontally moved door for protecting a door closing plane from obstacles and/or objects. For this purpose, a distance measurement scanning detector is arranged at the border of a monitored area, which provides detector beams in front of and behind the door closing plane for distance measurement and radiates them synchronously for providing a forked detector beam scanning system across the entire monitored area. The running time of these detector beams is compared with previously stored reference values, wherein the occurrence of an object in the monitored area results in a reduction of the running time, so that it may be detected in a reliable manner. Then, detector output signals are output to a control unit which causes the stopping and/or reversing of the motor drive.
But also these kinds of safeguarding of a dangerous place in the movement area of a door leaf with detection elements arranged in front of or behind the door closing plane are often not sufficient when persons approach and the door leaf is simultaneously moving. Thus, a particular reaction time of the safety system necessarily exists, so that it cannot be excluded reliably that, for instance, the head of a person and the leading edge or a large area of the door leaf possibly collide in the course of their movement. Furthermore, an immediate reversal of direction of the door leaf movement, as it is as a rule provided, may also constitute a further source of danger for the person, etc. being in the door closing area. As experience has shown, at least minor injuries due to abrasions on the head, above all on the forehead, the nose, and the ears, cannot always be avoided here.
In practice, depending on the site of installation, the dimension, and the mode of operation of the door arrangement, there are different kinds of risk situations for which respectively adapted safety systems exist. All of these, however, have their weak points, as explained above. To the extent that it is at all possible to combine the individual kinds of safety systems with each other in technical respect, this is partially also done. However, this results in a very high constructional effort with corresponding costs. Still, the risks given cannot be removed comprehensively and reliably therewith. Moreover, the conventional safety systems are, due to their relatively simply structured failure routines, adapted to always stop the door leaf movement in the case of doubt, which may result in impairments and time delays in the production process.